Stackable differential mobility analyzer for aerosol measurement

Abstract

A multi-stage differential mobility analyzer (MDMA) for aerosol measurements includes a first electrode or grid including at least one inlet or injection slit for receiving an aerosol including charged particles for analysis. A second electrode or grid is spaced apart from the first electrode. The second electrode has at least one sampling outlet disposed at a plurality different distances along its length. A volume between the first and the second electrode or grid between the inlet or injection slit and a distal one of the plurality of sampling outlets forms a classifying region, the first and second electrodes for charging to suitable potentials to create an electric field within the classifying region. At least one inlet or injection slit in the second electrode receives a sheath gas flow into an upstream end of the classifying region, wherein each sampling outlet functions as an independent DMA stage and classifies different size ranges of charged particles based on electric mobility simultaneously.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of and incorporates by reference in its entirety Provisional Application No. 60 / 685,933 filed on May 31, 2005.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]The United States Government has rights in this invention pursuant to Contract No. DE-AC05-00OR22725 between the United States Department of Energy and UT-Battelle, LLC.FIELD OF THE INVENTION[0003]The invention relates to methods and apparatus for sizing and classifying charged particle or ions based on differential mobility analysis.BACKGROUND OF THE INVENTION[0004]Particle size is a significant parameter for particles, which can be used to characterize the behavior of an aerosol. Particle sizes need to be measured in many situations. For example, particles formed in the semiconductor industry are critical for microcontamination control. Particles formed in chemical reactors are of great interest in material science. To obtain...

AI Technical Summary

Benefits of technology

[0012]In a preferred embodiment, the first electrode or grid is an inner electrode disposed within the second electrode. Such an arrangement provides an additional particle focusing effect described below. The MDMA can further comprise a flow laminarizor disposed between the inlet or injection slit for receiving the sheath gas flow and the classifying region, wherein the flow laminarizor distributes and laminates the sheath gas flow before entry into the classifying region.

[0016]In one embodiment, the MDMA is modularized, wherein the method further comprises the step of modifying a number or a length of the DMA stages. The method can further comprise the step of extracting aerosol flow from the MDA at a rate which evenly partitions a flowrate of said aerosol at each of said MDA stages. However, the flow rate for extracting monodisperse aerosol flow from each stage can be varied among the stages, depending on the application. In another embodiment, the extracted aerosol flow rate from the MDA can be equal to the flowrate of the aerosol. The method can further comprising the step of scanning the DC bias voltage. This enables higher resolution sizing measurements.

Problems solved by technology

Although this DMA works well in the size range of 20 to 500 nm, it becomes increasingly difficult to perform accurate measurement / classification for particles less than 10 nm.

ACLDMA, however, can only classify one particle size at a time as the conventional DMA.

Furthermore, mechanical wear can cause the concern of DMA axial alignment and gas leak.

DMS and EEPS do not have adequate resolution because the entire size range is divided into only 32 channels.

Furthermore, there is current leak between the adjacent electrodes, which can interfere with the measurement of particle size distribution.

The current leak makes it impossible to measure liquid particles.

Due to the detection limit of the electrometer, DMS and EEPS can only measure high concentration aerosol.

Therefore DMS and EEPS cannot be used to scan particle size distribution in the same way as DMA.

Since no sampling flow is drawn out of the instruments, it is impossible to determine their transfer function experimentally.

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